Most often by citrus in perfumery we describe the whole spectrum of hesperidic fruits (Hesperidia), named after the Hesperides, nymphs from Greek mythology. These are fruits or citrus-smelling raw materials (notably verbena and lemongrass) and a few are among the most ancient ingredients in perfumery alongside resins. The more modern variations, such as pomelo, grapefruit, yuzu and hassaku, are relatively recent developments in the area of perfume extraction. The citrus essences are expressed or cold-expressed in most cases to preserve their inherent freshness. Petitgrain is an exception, as it comes from the steam distillation of the twigs and leaves of the bitter orange tree. Citruses provide a refreshing and effarvescent quality to fragrances, accounting for the top note which tickles our noses with pleasure. They're helpful for clearing one's mind and feel sunny and optimistic, lending an air of easy elegance and cleanness. Bergamot especially is an integral part of the classic Eau de Cologne formula. Citruses are a classic companion to more tenacious floral and resinous notes in oriental fragrances and they also provide a good companion to other fruity notes, cutting the sugar and injecting tartness.